Three dimensional printers can use many and varied techniques to make a physical object from a computer model. In general, the computer model is converted to a fabrication-ready representation containing tool instructions for a printer to arrange a build material into the physical object. But this transformation from the computer model to the physical object is an imperfect one, subject as it is to the peculiarities of the particular fabrication processes that are used. While the outside appearance is generally well preserved, the interior spaces may be filled with a variety of relatively arbitrary structures with little regard for the structural integrity of the resulting object. This works fine in many circumstances. But where the physical object is destined for functional rather than aesthetic ends—a machine gear instead of a display piece—the geometry of the fabrication-ready representation might contain structural deficiencies that render the physical object unsuitable for its intended purpose. There remains a need for structural analysis in the process of converting three-dimensional models to fabrication-ready representations.